JP5921511B2 - Radiation image reading apparatus, radiation image reading program, and radiation image reading method - Google Patents

Description

  The present invention relates to a radiation image reading apparatus, a radiation image reading program, and a radiation image reading method.

  When a stimulable phosphor (stimulable phosphor) is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, electron beams, etc.), a part of the radiation energy is accumulated in the stimulable phosphor. Is done. Thereafter, when the stimulable phosphor is irradiated with excitation light such as laser light, the stimulable phosphor emits light in accordance with the accumulated energy.

  In general, a radiation image reading apparatus using a stimulable phosphor is used for medical and industrial nondestructive inspection. In the radiographic image reading apparatus, image information of a radiographic image of a subject such as a welded portion is temporarily recorded on a sheet (image plate: stimulable phosphor sheet) having a stimulable phosphor layer to excite the stimulable phosphor sheet IP. The stimulated light emitted by scanning with light is read photoelectrically.

  For example, in Patent Document 1, a storage phosphor sheet for normal resolution and a storage phosphor sheet for high resolution are used. When reading at high resolution, the surface of the storage phosphor sheet is irradiated with excitation light. A radiation image reading apparatus that rotates a polygon mirror at a high speed when rotating a polygon mirror at a low speed and reading at a low resolution is described.

  On the other hand, it is required to remove unevenness (scanning unevenness) generated in a radiographic image. Patent Document 2 discloses a technique for removing linear unevenness by image correction from an original image having linear unevenness read by a radiation image reading device as a technique for removing stripe unevenness (linear unevenness) in a radiographic image. Is described.

JP 2004-163792 A JP 2010-239480 A

  In the technique described in Patent Document 2, since unevenness is removed on the image data by image correction, there is a possibility that a part to be inspected may be erased by mistake. For example, when the site to be inspected is a weld defect or the like, the defect is linear, and thus may be corrected as unevenness.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radiation image reading apparatus, a radiation image reading program, and a radiation image reading method that have high image quality and small scanning unevenness. To do.

In order to achieve the above object, the radiation image reading apparatus of the present invention has a common beam diameter on the surface of the stimulable phosphor sheet regardless of the resolution with respect to the stimulable phosphor sheet on which the radiation image is accumulated and recorded. A scanning unit that scans certain excitation light and photoelectrically reads the photostimulated luminescence emitted from the stimulable phosphor sheet that has been irradiated with the excitation light. when reading at a first resolution is greater than the beam diameter size, the first scanning rate, and read with excitation light of a first intensity, high-resolution der than the first resolution is, the pixel size of the excitation light When reading at a second resolution smaller than the beam diameter size, control is performed to read with excitation light having a second scanning speed slower than the first scanning speed and a second intensity smaller than the first intensity. control It includes a stage, a.

  The second intensity in the radiographic image reading apparatus of the present invention is preferably 2.0 mW or more on the surface of the stimulable phosphor sheet.

  In addition, the second intensity on the surface of the stimulable phosphor sheet in the radiation image reading apparatus of the present invention is preferably 30% or less of the first intensity on the surface of the stimulable phosphor sheet.

  In the radiographic image reading apparatus of the present invention, it is preferable that the beam diameter size of the excitation light is 30 μm, the pixel size of the first resolution is 100 μm, and the pixel size of the second resolution is 25 μm.

  The radiographic image reading program of the present invention is for causing a computer to function as control means of the radiographic image reading apparatus of the present invention.

In the radiographic image reading method of the present invention, excitation light having a beam diameter common to the surface of the stimulable phosphor sheet regardless of the resolution is applied to the stimulable phosphor sheet on which the radiographic image is accumulated and recorded by the control means. First, the pixel size is larger than the beam diameter size of the excitation light with respect to the reading means that photoelectrically reads the stimulated emission light generated from the stimulable phosphor sheet that has been scanned by the scanning means and irradiated with the excitation light. when reading in the resolution, the first scanning rate, and read with excitation light of a first intensity, than the first resolution Ri high resolution der, the pixel size is smaller than the beam diameters of the pumping light 2 In the case of reading at a resolution of 1, a step of performing control for reading with excitation light having a second scanning speed slower than the first scanning speed and a second intensity lower than the first intensity is provided.

  According to the present invention, it is possible to obtain an effect that high image quality and scanning unevenness can be reduced.

It is a longitudinal cross-sectional view which shows schematic structure of the radiographic image reading apparatus 10 which reads the image information of the radiographic image recorded on the stimulable fluorescent substance sheet IP of this Embodiment. It is a top view which shows an example of a structure of the excitation light scanning unit which concerns on this Embodiment. It is a side view which shows an example of a structure of the excitation light scanning unit which concerns on this Embodiment. It is explanatory drawing for demonstrating scanning nonuniformity, and is a conceptual diagram showing the scanning nonuniformity which generate | occur | produces in the read radiographic image. It is explanatory drawing for demonstrating scanning nonuniformity, and is explanatory drawing which showed the image density (QL value) of the subscanning direction of the radiographic image which the scanning nonuniformity of FIG. 3A produced. It is an example of the schematic diagram of the main structures for suppressing generation | occurrence | production of the scanning nonuniformity in the radiographic image reading apparatus of this Embodiment. It is a graph which shows an example of the correspondence of the intensity | strength of excitation light and scanning unevenness intensity | strength (QL value) in a high resolution mode and a low resolution mode. It is explanatory drawing which shows an example of the correspondence of the intensity | strength of excitation light and scanning nonuniformity in a high resolution mode. It is explanatory drawing which shows an example of the correspondence of the intensity | strength of the excitation light and scanning nonuniformity in a low resolution mode. It is explanatory drawing for demonstrating the correspondence of the beam diameter of excitation light and pixel size in the stimulable phosphor sheet | seat IP surface, and has shown the case where the beam diameter of excitation light is larger than pixel size. It is explanatory drawing for demonstrating the correspondence of the beam diameter of excitation light and pixel size in the stimulable phosphor sheet | seat IP surface, and has shown the case where the beam diameter of excitation light is smaller than pixel size. It is a graph which shows an example of the correspondence of the intensity | strength of excitation light and the S / N ratio of a radiographic image in a high resolution mode, and shows an example of the correspondence with excitation light intensity. It is explanatory drawing which shows an example of the correspondence of the intensity | strength of excitation light and the S / N ratio of a radiographic image in a high resolution mode, and shows an example of the correspondence of the intensity | strength of excitation light and S / N ratio. It is a graph which shows an example of the correspondence of the beam diameter of excitation light in high resolution mode, and resolution. It is explanatory drawing which shows each condition in the high resolution mode in the radiographic image reading apparatus of this Embodiment, and each condition in a low resolution mode. It is a flowchart showing the flow of an example of the reading control process performed by the control part of the radiographic image reading apparatus of this Embodiment.

  Hereinafter, an example of the present embodiment will be described with reference to the drawings.

  First, a schematic configuration of the radiation image reading apparatus according to the present embodiment will be described. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a radiation image reading apparatus 10 that reads image information (hereinafter referred to as “radiation image information”) of a radiation image recorded on the stimulable phosphor sheet IP. Examples of the radiation image reading apparatus 10 according to the present embodiment include a radiation image reading apparatus that reads radiation image information recorded on the stimulable phosphor sheet IP in an industrial CR (Computed Radiography) system or the like. It is done.

  As shown in FIG. 1, a touch panel 32 having functions of an operation unit and a monitor is provided on an upper portion of a housing 30 that forms the outer shape of the radiation image reading apparatus 10. Below the touch panel 32, a plurality of, for example, four cassettes 34, which are detachable cassette loading portions 36a to 36d, are provided.

  The cassette 34 includes a rectangular case 40 that accommodates the stimulable phosphor sheet IP, and a lid 44 that allows the opening 42 of the case 40 to be opened and closed.

  Each of the cassette loading portions 36a to 36d is provided with a support base 46 for placing the cassette 34 thereon. In addition, in the cassette loading portions 36a to 36d, shutter members 48 for shielding the inside of the housing 30 are disposed so as to be freely opened and closed. Further, a cassette position fixing mechanism (not shown) for fixing the position of the cassette 34 and a lid opening / closing mechanism (not shown) for opening and closing the lid 44 of the cassette 34 are incorporated in the cassette loading sections 36a to 36d. .

  Further, the elevating leaf unit 50 is mounted inside the cassette loading portions 36a to 36d. The ascending / descending sheet portion 50 is arranged corresponding to any one of the cassette loading portions 36a to 36d, and takes out the stimulable phosphor sheet IP from the arbitrary cassette 34, while the stimulable phosphor sheet IP after reading and erasing. Has a function of returning the product to the cassette 34. The ascending / descending sheet unit 50 is capable of moving up and down the sheet body sheet mechanism 52 including a roller for conveying each of the stimulable phosphor sheets IP and the sheet body sheet mechanism 52 in the vertical direction (arrow A direction). And an elevating mechanism 54.

  A main conveyance path 60 for conveying the stimulable phosphor sheet IP is connected to the sheet-body sheet mechanism 52 of the ascending / descending sheet portion 50. The main conveyance path 60 extends downward from the ascending / descending sheet 50, then curves at the lower portion of the housing 30, extends in the horizontal direction, and reaches the reading conveyance path 70. Note that the first roller pair 80 and the second roller pair 82 constituting the reading conveyance path 70 sandwich the stimulable phosphor sheet IP and convey it in the sub-scanning direction in the arrow Y direction. Note that the first roller pair 80 and the second roller pair 82 of the present embodiment use rollers whose outer peripheral surfaces are made of rubber.

  The reading conveyance path 70 is curved and extends upward, and then continues to a retreat conveyance path 94 extending in the horizontal direction. Further, one end of the erasing conveyance path 96 is continuous between the reading conveyance path 70 and the retreat conveyance path 94. The other end of the erasing conveyance path 96 is continuous with the main conveyance path 60, and supplies the stimulable phosphor sheet IP conveyed from the evacuation conveyance path 94 to the main conveyance path 60.

  An excitation light scanning unit 64 and an upper reading unit 66 are disposed on the inner peripheral upper side of the reading conveyance path 70 that curves upward.

  2A and 2B are configuration diagrams showing an example of the configuration of the excitation light scanning unit 64. 2A shows a plan view of the excitation light scanning unit 64, and FIG. 2B shows a side view of the excitation light scanning unit 64.

  As shown in FIGS. 2A and 2B, the excitation light scanning unit 64 includes a light source 12 and a diverging lens system for making the excitation light L, which is a light beam emitted from the light source 12, into divergent light. 13. The excitation light L becomes divergent light by the diverging lens system 13. Examples of the light source 12 include a laser diode.

  The excitation light scanning unit 64 includes a rotating polygon mirror 14 for reflecting and deflecting the excitation light L diverged by the diverging lens system 13 toward the surface (scanning surface) of the stimulable phosphor sheet IP, and the rotating polygon mirror 14. The first lens 16 and the second lens 17 that are arranged in the subsequent stage and are included in the scanning imaging optical system that images the excitation light L on the stimulable phosphor sheet IP, and the excitation light L on the stimulable phosphor sheet IP. And a reflection mirror 18 for reflecting toward the screen.

  According to the excitation light scanning unit 64, the excitation light L emitted from the light source 12 is once converted into divergent light by the diverging lens system 13, and then reflected by the deflection surface provided on the outer peripheral surface of the rotary polygon mirror 14. The

  The excitation light L reflected by the deflecting surface of the rotary polygon mirror 14 passes through the first lens 16 and the second lens 17 and is reflected by the reflection mirror 18 to form an image on the stimulable phosphor sheet IP. Scanning exposure is performed on the phosphor sheet IP in the main scanning direction. On the other hand, the stimulable phosphor sheet IP is driven by the driving means (see FIG. 1) in the sub-scanning direction intersecting with the main scanning direction in which the excitation light L scans. The surface is scanned with the excitation light L. From the stimulable phosphor sheet IP irradiated with the excitation light L, stimulated emission light including radiation image information is output.

  The upper reading unit 66 includes a light collecting guide 84 and a photoelectric converter 86. The condensing guide 84 includes a transparent body such as an acrylic plate, the incident surface at the lower end of which is disposed close to the first roller pair 80 and the second roller pair 82. The photoelectric converter 86 includes a photomultiplier or the like connected to the emission surface at the upper end of the light collecting guide 84.

  Further, a condensing mirror 88 is disposed in the vicinity of the incident surface of the condensing guide 84 in order to efficiently guide the stimulated emission light R to the incident surface. The photoelectric converter 86 converts the stimulated emission light introduced through the light collection guide 84 into an electrical signal.

  In the present embodiment, as shown in FIG. 1, the photoelectric converter 86 is covered with a magnetic shield material 90 except for the light incident portion (photoelectric surface). For example, a material with high magnetic permeability is suitable as the magnetic shield material 90. Specifically, permalloy, a directional silicon steel plate, an iron plate (pure iron), or the like can be used. Also good. Permalloy is most suitable as the magnetic shield material 90.

  Between the evacuation conveyance path 94 and the erasure conveyance path 96, the control circuit 120 that controls the entire radiation image reading apparatus 10 and the radiation energy remaining in the stimulable phosphor sheet IP from which the radiation image information has been read. An erasing unit 122 for erasing is provided. The erasing unit 122 accommodates a plurality of erasing light sources 126 such as cold cathode fluorescent tubes in a case 124.

  Next, the flow of a reading operation for reading a radiation image from the stimulable phosphor sheet IP by the radiation image reading device 10 will be described.

In the present embodiment, the conveyance direction in the radiation image reading apparatus 10 is in the longitudinal direction of the stimulable phosphor sheet IP (radiation image recorded on the stimulable phosphor sheet IP) (FIG. 3A, arrow L1 direction). This corresponds to the sub-scanning direction. Further, the direction (in FIG. 3A, the direction of arrow W1) intersecting the longitudinal direction of the stimulable phosphor sheet IP is the main scanning direction. The stimulable phosphor sheet IP is directed downward to the cassette 34. Then, the cassette 34 is loaded into the cassette loading portions 36a to 36d (see FIG. 1).

  The cassette 34 loaded in the cassette loading sections 36 a to 36 d is fixed in position by a mechanism for fixing the position of the cassette 34, and then the lid body 44 of the cassette 34 is opened. The body sheet IP is separated from the cassette 34. The stored phosphor sheet IP is conveyed by the main conveyance path 60 and supplied to the reading conveyance path 70.

  The reading and conveying path 70 sandwiches the stimulable phosphor sheet IP between the first and second roller pairs 80 and 82, and conveys the accumulating phosphor sheet IP in the arrow Y direction.

  On the other hand, the excitation light scanning unit 64 disposed in the upper part of the reading conveyance path 70 deflects the excitation light L output from the light source 12 in the main scanning direction by the rotary polygon mirror 14 and accumulates the stimulable phosphor sheet IP. The phosphor layer (not shown) is scanned. The stimulable phosphor layer of the stimulable phosphor sheet IP irradiated with the excitation light L outputs stimulated emission light including radiation image information.

  The stimulated emission light output from the stimulable phosphor layer of the stimulable phosphor sheet IP is directly incident on the incident surface of the condensing guide 84 provided in the upper reading unit 66 or is reflected by the condensing mirror 88. After being incident on the incident surface, the light is guided from the exit surface to the photoelectric converter 86 and converted into an electrical signal.

  The electrical signal related to the radiation image information obtained by the photoelectric converter 86 is transferred to an external device or the like via the control circuit 92 and a wired or wireless communication line.

  The storage phosphor sheet IP that has been read is once transported from the reading transport path 70 to the evacuation transport path 94 and then supplied to the erasing transport path 96. In addition, while the stimulable phosphor sheet IP that has been read is temporarily transported to the evacuation transport path 94, another stimulable phosphor sheet IP may be supplied to the read transport path 70 and read in parallel. it can.

  The storable phosphor sheet IP supplied to the erasing transport path 96 is irradiated with the erasing light Q from the erasing light source 126 provided in the erasing unit 122 to the stimulable phosphor layer, and the radiation remaining in the storable phosphor layer. The image information is deleted. The storable phosphor sheet IP after erasure is transported to the lift sheet 50 via the main transport path 60 and then returned to the desired cassette 34.

  The radiation image reader 10 may cause unevenness (scanning unevenness) due to density variation in the radiation image based on the radiation image information recorded on the stimulable phosphor sheet IP. 3A and 3B are explanatory diagrams for explaining scanning unevenness. FIG. 3A is a conceptual diagram showing scanning unevenness that occurs in the read radiation image. FIG. 3B is an explanatory diagram showing the image density (QL value) in the sub-scanning direction of the radiation image in which the scanning unevenness in FIG. 3A occurs. As shown in FIGS. 3A and 3B, the scanning unevenness occurs along the main scanning direction of the radiation image. In scanning unevenness, the image density (QL value) increases.

  The causes of unevenness in scanning include fluctuations in the rotational speed of a motor (not shown) used to convey the stimulable phosphor sheet IP, and roller pairs 80 and 82 used to convey the stimulable phosphor sheet IP. And the like, the load fluctuation when the stimulable phosphor sheet IP enters the roller pair 80, 82, the load fluctuation when the roller pair 80, 82 exits, and the like.

  For example, in an industrial CR, there is a strict requirement for scanning unevenness that occurs in a radiographic image because the image is reduced or enlarged on the monitor or the gradation is extremely raised. However, when the scanning unevenness is removed from the image data by image correction, there is a possibility that the part to be inspected may be erased by mistake. For example, when the site to be inspected is a welded part defect or the like, the defect is linear, so that the image may be corrected as scanning unevenness, and the defect is removed from the finally obtained radiographic image.

  Therefore, in the radiation image reading apparatus 10 of the present embodiment, the occurrence of scanning unevenness is suppressed when the radiation image information is read. Specifically, in the radiation image reading apparatus 10, the control circuit 120 controls the driving of the excitation light scanning unit 64 to control the power of the excitation light, thereby suppressing the occurrence of scanning unevenness. FIG. 4 shows an example of a schematic diagram of a main configuration for suppressing the occurrence of scanning unevenness in the radiation image reading apparatus 10 of the present embodiment.

  As shown in FIG. 4, the control circuit 120 includes a control unit 20, a resolution setting unit 22, a light source control unit 24, a motor drive circuit 26, and an I / F unit 28. The control unit 20, the resolution setting unit 22, the light source control unit 24, the motor drive circuit 26, and the I / F unit 28 are connected to each other via a bus 29 so that various information can be exchanged.

  The control unit 20 includes a microcomputer, and includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). In the control unit 20 of the present embodiment, the CPU executes a program stored in the ROM, so that a reading control process, which will be described in detail later, is executed. Note that the control unit 20 is not limited to the configuration illustrated in FIG. 4, and may be realized by, for example, an ASIC (Application Specific Integrated Circuit) or a programmable logic device.

  The resolution setting unit 22 is set with a resolution for reading a radiation image. In the radiographic image reading apparatus 10 according to the present embodiment, two modes, a high resolution mode and a low resolution mode, are provided as radiographic image reading resolutions. The high resolution mode has a higher resolution than the low resolution mode. Specifically, the pixel size is 25 μm / pixel. The low resolution mode has a lower resolution than the high resolution mode. Specifically, the pixel size is 100 μm / pixel, and the low resolution mode has a larger pixel size than the high resolution mode. The pixel size means a value obtained by dividing the scanning width on the stimulable phosphor sheet IP by the number of pixels in both the main scanning direction and the sub-scanning direction. Further, in the radiation image reading apparatus 10 of the present embodiment, the reading speed in the high resolution mode is lower than that in the low resolution mode.

  When the user designates the resolution via the touch panel 32 or the I / F unit 28 provided on the upper part of the radiation image reading apparatus 10, the designated resolution (high resolution mode or low resolution mode) is set in the resolution setting unit 22. Is done.

  The light source control unit 24 has a function of controlling the light source 12 of the excitation light scanning unit 64. In the present embodiment, the control unit 20 controls the light source control unit 24 to control the intensity (laser power) of the excitation light of the light source 12. The method for controlling the intensity of the excitation light is not particularly limited. For example, when the light source 12 is a laser diode, the current value of the drive current may be controlled.

  The motor drive circuit 26 has a function of driving (rotating) the rotary polygon mirror 14 of the excitation light scanning unit 64. In the present embodiment, the rotational speed of the rotary polygon mirror 14 is controlled by controlling the motor drive circuit 26 by the control unit 20. In the radiation image reading apparatus 10 of the present embodiment, the scanning speed of scanning the surface of the stimulable phosphor sheet IP in the sub-scanning direction is controlled to control the reading speed (sampling speed) of the radiation image. Specifically, the control unit 20 controls the rotational speed of the rotary polygon mirror 14. In the present embodiment, the rotational speed of the rotary polygon mirror 14 is represented by the number of rotations (rpm). The greater the number of revolutions, the faster the rotational speed and the faster the scanning speed. On the other hand, the smaller the number of revolutions, the slower the rotational speed and the slower the scanning speed. The I / F unit 28 is an interface for exchanging information with an external device.

  The occurrence of scanning unevenness in the high resolution mode and the occurrence of scanning unevenness in the low resolution mode will be described. 5A to 5C show an example of a correspondence relationship between the intensity of excitation light and the scanning unevenness intensity (QL value) in the high resolution mode and the low resolution mode. FIG. 5A is a graph showing an example of a correspondence relationship between the intensity of excitation light and the scanning unevenness intensity (QL value) in the high resolution mode and the low resolution mode. FIG. 5B is an explanatory diagram illustrating an example of a correspondence relationship between the intensity of excitation light and scanning unevenness in the high resolution mode. FIG. 5C is an explanatory diagram illustrating an example of a correspondence relationship between the intensity of excitation light and scanning unevenness in the low resolution mode.

  Note that the stimulable phosphor sheet IP used in the present embodiment is one having a stimulable phosphor of BaFX: Eu2 +; X = Br and I). In the case of the high resolution mode, as a specific example, FU-1 manufactured by FUJIFILM Corporation and UR-1 for Fujifilm Imaging Plate Industry is used. In the case of the low resolution mode, as a specific example, Fuji Film Co., Ltd. ST-VI for Fujifilm Imaging Plate Industry is used.

  The reading conditions in the high-resolution mode are a pixel size of 25 μm / pixel, a scanning speed (reading speed) of 0.7 μsec / pixel, a wavelength of excitation light of 660 nm, and a beam diameter at a half-value width of excitation light of 30 μm. . The reading conditions in the low resolution mode are a pixel size of 100 μm / pixel, a scanning speed (reading speed) of 1.0 μsec / pixel, a wavelength of excitation light of 660 nm, and a beam diameter at a half-value width of excitation light of 30 μm. . As described above, in the radiation image reading apparatus 10 of the present embodiment, the wavelength and beam diameter of the excitation light are the same regardless of the high resolution mode and the low resolution mode. In the present embodiment, the beam diameter defined by the half-value width of the excitation light on the surface of the stimulable phosphor sheet IP is described as “beam diameter”.

  As shown in FIGS. 5A to 5C, in any of the high resolution mode and the low resolution mode, when the intensity of excitation light increases, the intensity of scanning unevenness (QL value) increases. When the intensity is small, the intensity of scanning unevenness (QL value) becomes small. The correspondence between the intensity of the excitation light and the intensity of scanning unevenness is considered to be a characteristic unique to the stimulable phosphor sheet IP. When the excitation light intensity is the same, the scanning unevenness intensity (QL value) is smaller in the low resolution mode than in the high resolution mode.

  As shown in FIGS. 5A to 5C, regarding the scanning unevenness, if the intensity of the excitation light is the same, the beam diameter of the excitation light is larger when the beam diameter of the excitation light is larger than the pixel size. Tends to be more visible than when the pixel size is smaller than the pixel size. One example of this is as follows.

  In the radiation image reading apparatus 10 according to the present embodiment, the excitation light emitted from the excitation light scanning unit 64 is scanned according to the reading pixel. 6A and 6B are explanatory diagrams for explaining the correspondence between the beam diameter of the excitation light and the pixel size on the surface of the stimulable phosphor sheet IP. FIG. 6A shows a case where the beam diameter of the excitation light is larger than the pixel size. FIG. 6B shows a case where the beam diameter of the excitation light is smaller than the pixel size.

  As shown in FIG. 6A, when the beam diameter of the excitation light is larger than the pixel size, the excitation light irradiated when the nth line (pixel row) is read on the surface of the stimulable phosphor sheet IP. And the excitation light irradiated when the (n + 1) th line (pixel row) is read overlap, and scanning unevenness is likely to occur. On the other hand, as shown in FIG. 6B, when the beam diameter of the excitation light is smaller than the pixel size, the surface of the stimulable phosphor sheet IP was irradiated when the nth line (pixel row) was read. The excitation light and the excitation light irradiated when the n + 1th line (pixel row) is read do not overlap.

  When the beam diameter of the excitation light is larger than the pixel size, as shown in FIG. 6A, the stimulable phosphor sheet IP in the overlapping portion is irradiated with the excitation light twice. Scanning unevenness becomes easier to visually recognize than when the beam diameter of light is smaller than the pixel size.

  In general, if the intensity of scanning unevenness (QL value) is 10 or less, it is difficult to visually recognize even if scanning unevenness occurs on a radiographic image, and the intensity of scanning unevenness (which has little influence on interpretation of a subject image) ( When the intensity of the excitation light when the QL value is 10 is calculated from the graph shown in FIG. 5A, the high resolution mode is 9.7 mW and the low resolution mode is 32 mW. The intensity of the excitation light in the high resolution mode is about 30% with respect to the intensity of the excitation light in the low resolution mode.

  Therefore, in the low resolution mode, when the scanning unevenness is not a problem, for example, as described above, the scanning unevenness intensity (QL value) is 10 or less, the high resolution mode is compared with the excitation light intensity in the low resolution mode. If the intensity of the excitation light is 30% or less, the occurrence of uneven scanning can be suppressed even in the high resolution mode.

  In the radiographic image reading apparatus 10 according to the present embodiment, the control unit 20 controls the intensity of the excitation light in the high resolution mode and the low resolution mode as described above, thereby suppressing the occurrence of scanning unevenness. According to FIGS. 5A to 5C, the intensity of the excitation light is preferably 2.0 W or less from the viewpoint of uneven scanning.

  On the other hand, the higher the intensity of the excitation light, the higher the S / N ratio and the higher the quality of the radiation image. FIG. 7A and FIG. 7B show an example of a correspondence relationship between the intensity of the excitation light and the S / N ratio of the radiation image in the high resolution mode. FIG. 7A is a graph showing an example of a correspondence relationship with the intensity of excitation light. FIG. 7B is an explanatory diagram illustrating an example of a correspondence relationship between the intensity of excitation light and the SN ratio. 7A and 7B, the conditions in the high resolution mode are the same as described above.

  As an image quality based on ISO 17636-2 (welding), it is preferable that the S / N ratio of a radiographic image used for inspection of welding defects is 80 or more. Taking into account manufacturing variations and the like, the S / N ratio of the radiographic image is more preferably 100 or more.

  It can be seen from FIGS. 7A and 7B that the intensity of the excitation light needs to be 2.0 mW or more in order to make the SN ratio of the radiation image 100 or more. Even in the low resolution mode, if the intensity of the excitation light is 2.0 mW or higher, the SN ratio of the radiographic image is 100 or higher as in the high resolution mode.

  Note that when the intensity of the excitation light increases, the effect of increasing the intensity of scanning unevenness increases as described above (see FIG. 5A) rather than the effect of improving the SN ratio. From A) and FIG. 7B, the upper limit of the intensity of the excitation light is preferably 9.7 mW or less.

  In the high resolution mode, the beam diameter of the excitation light is preferably as small as possible in order to increase the resolution, but it is included in the scanning imaging optical system of the excitation light scanning unit 64 in order to reduce the beam diameter. There is a need to increase the number of lenses, which leads to an increase in cost. Therefore, in the radiation image reading apparatus 10 of the present embodiment, the beam diameter of the excitation light is made larger than the pixel size in the high resolution mode in order to reduce the cost. By determining the size of the beam diameter according to the resolution in the high resolution mode, both high resolution and low cost can be achieved.

  FIG. 8 shows an example of a correspondence relationship between the beam diameter of the excitation light and the resolution in the high resolution mode. In FIG. 8, each condition in the high resolution mode is the same as the above except that the intensity of the excitation light is 2.0 mW and the beam diameter is arbitrary.

  In general, with regard to the resolution of industrial CR, it is required to measure the resolution performance with two wires called Duplex Wire defined by EN462-5. In the case of inspecting a welded portion, the resolution is required to be 20% or more under DD13 (conditions for opening a 50 μm wire by 50 μm). According to FIG. 8, in the high resolution mode with a pixel size of 25 μm, if the beam diameter is 36 μm or less, the required resolution of 20% or more can be obtained. For these reasons, in the radiation image reading apparatus 10 of the present embodiment, the beam diameter is 30 μm regardless of the resolution (mode), and the pixel size in the high resolution mode is 25 μm.

  From the above, in the radiation image reading apparatus 10 according to the present embodiment, the control unit 20 performs scanning by performing reading control processing in which the intensity of the excitation light is reduced in the high resolution mode compared to the low resolution mode. Reduces the occurrence of unevenness. FIG. 9 shows each condition in the high resolution mode and each condition in the low resolution mode in the radiation image reading apparatus 10 of the present embodiment. In the radiographic image reading apparatus 10 according to the present embodiment, each of these conditions is stored in advance in the HDD of the control unit 20 or the resolution setting unit 22.

  FIG. 10 is a flowchart showing an example of a reading control process executed by the control unit 20 of the radiation image reading apparatus 10 according to the present embodiment. The reading control process shown in FIG. 10 is executed when the radiation image information is read from the stimulable phosphor sheet IP, such as when an instruction to read the radiation image information is given. Note that the reading control process shown in FIG. 10 is executed by the CPU of the control unit 20 executing a program stored in the ROM.

  In step S100, the control unit 20 acquires the resolution. When the resolution is set in the resolution setting unit 22, either the high resolution mode or the low resolution mode is acquired. When the resolution is instructed via the I / F unit 28 or the like, the resolution (either the high resolution mode or the low resolution mode) is acquired based on the instruction.

  In the next step S102, the control unit 20 determines whether or not the high resolution mode is set. In the case of the low resolution mode, the control unit 20 proceeds from step S102 to step S106. In step S106, the control unit 20 determines the scanning speed (first scanning speed) and the intensity (first intensity) of excitation light in the low resolution mode. As shown in FIG. 9, the control unit 20 of the present embodiment determines that the scanning speed is 1.0 μsec / pixel and the intensity of the excitation light is 20 mW in the low resolution mode.

  On the other hand, in the case of the high resolution mode, the process proceeds from step S102 to step S104. In step S104, the control unit 20 determines the scanning speed (second scanning speed) and the intensity (second intensity) of excitation light in the high resolution mode. As shown in FIG. 9, the control unit 20 according to the present embodiment determines that the scanning speed is 0.7 μsec / pixel and the intensity of the excitation light is 2.0 mW in the high resolution mode. That is, in the case of the high resolution mode, the scanning speed is determined to be slower than that in the low resolution mode (second scanning speed <first scanning speed). In the high resolution mode, the intensity of the excitation light is determined to be smaller than that in the low resolution mode (second intensity <first intensity).

  In step S108 subsequent to step S104 and step S106, the control unit 20 instructs the determined scanning speed and excitation light intensity, and then ends the reading control process. The controller 20 instructs the motor drive circuit 26 on the determined scanning speed. The motor drive circuit 26 drives (rotates) the rotary polygon mirror 14 based on the instruction. Further, the control unit 20 instructs the light source control unit 24 on the determined intensity of the excitation light. The light source control unit 24 controls the light emission of the light source 12 based on the instruction.

  As described above, in the radiation image reading apparatus 10 of the present embodiment, the high resolution mode (pixel size: 25 μm / pixel) and the low resolution mode (pixel size 100 μm) are used as modes for reading radiation image information from the stimulable phosphor sheet IP. / Pixel) is provided. The control unit 20 makes the intensity of the excitation light smaller in the high resolution mode than in the case of reading the radiation image information in the low resolution mode. Further, the control unit 20 makes the scanning speed slower in the high resolution mode than in the case of reading the radiation image information in the low resolution mode. As a specific example, in the high resolution mode, the rotational speed of the rotary polygon mirror 14 is set to 812 r. p. m, the scanning speed (reading speed) is 0.7 μsec, and the intensity of the excitation light is 2.0 mW. In the low resolution mode, the rotational speed of the rotary polygon mirror 14 is set to 2273r. p. m, the scanning speed (reading speed) is 1.0 μsec, and the intensity of the excitation light is 20 mW.

  As described above, in the radiation image reading apparatus 10 according to the present embodiment, the intensity of the excitation light is switched between the high resolution mode and the low resolution mode, and the high resolution mode is more effective than the low resolution mode. Since the intensity is small, it is possible to suppress scanning unevenness that occurs in the radiation image.

  Therefore, according to the radiation image reading apparatus 10 of the present embodiment, it is possible to suppress the scanning unevenness of the radiation image without removing the scanning unevenness on the image data by image correction. According to the radiation image reading apparatus 10 of the present embodiment, scanning unevenness does not have to be removed on the image data by image correction, and therefore there is no possibility that the inspection target region is accidentally erased by image correction.

  Further, in the radiation image reading apparatus 10 of the present embodiment, the intensity of the excitation light in the high resolution mode is 30% or less with respect to the intensity of the excitation light in the low resolution mode. Can be suppressed appropriately.

  Further, in the radiation image reading apparatus 10 of the present embodiment, since the intensity of the excitation light in the high resolution mode is 2.0 mW, it is possible to appropriately suppress the occurrence of uneven scanning and obtain a high S / N ratio. Can do.

  In the radiation image reading apparatus 10 of the present embodiment, the pixel size <excitation beam diameter in the high resolution mode, and the pixel size> excitation light beam diameter in the low resolution mode. Further, in the high resolution mode, the pixel size is 25 μm and the beam diameter is 30 μm. Thereby, it is possible to achieve both high resolution and low cost in the high resolution mode.

  In each of the above embodiments, the case where the reading control processing program is stored in advance in the control unit 20 of the radiation image reading apparatus 10 has been described. However, a flexible disk, a DVD (Digital Versatile Disk), a magneto-optical disk, It may be acquired from a recording medium such as a USB (Universal Serial Bus) memory, an external device, or the like and stored. In the present embodiment, the reading control process is realized by software processing, but may be realized by hardware resources.

  Moreover, in this Embodiment, the radiation of this invention is not specifically limited, X-ray, a gamma ray, etc. can be applied.

  The configurations, operations, and the like of the radiation image reading apparatus 10, the excitation light scanning unit 64, the upper reading unit 66, the control circuit 120, and the like described in the present embodiment are examples, and are within the scope not departing from the gist of the present invention. It goes without saying that it can be changed according to the situation.

DESCRIPTION OF SYMBOLS 10 Radiation image reader 14 Rotating polygon mirror 20 Control part 24 Light source control part 26 Motor drive circuit 64 Excitation light scanning unit 66 Upper reading unit IP Storage phosphor sheet

Claims (6)

For the stimulable phosphor sheet on which the radiation image is accumulated and recorded , the excitation light having the same beam diameter on the surface of the stimulable phosphor sheet regardless of the resolution is scanned by the scanning means , and irradiated with the excitation light. Reading means for photoelectrically reading the photostimulated luminescence generated from the stimulable phosphor sheet;
In the case where the reading means reads with a first resolution whose pixel size is larger than the beam diameter size of the excitation light , the reading means reads with the excitation light having the first scanning speed and the first intensity, Ri higher resolution der than the resolution, if the pixel size is read at a small second resolution than the beam diameters of the excitation light, the slower than the first scanning rate second scan speed, and the first Control means for performing control to read with excitation light having a second intensity smaller than the intensity of
A radiation image reading apparatus comprising: The second intensity is 2.0 mW or more on the surface of the stimulable phosphor sheet.
The radiation image reading apparatus according to claim 1 . The second intensity at the surface of the stimulable phosphor sheet is 30% or less of the first intensity at the surface of the stimulable phosphor sheet.
The radiographic image reading apparatus according to claim 1 . A beam diameter size of the excitation light is 30 μm, a pixel size of the first resolution is 100 μm, and a pixel size of the second resolution is 25 μm;
The radiographic image reading apparatus according to claim 3 . A radiographic image reading program for causing a computer to function as control means of the radiographic image reading apparatus according to any one of claims 1 to 4 . The control means scans the stimulable phosphor sheet on which the radiographic image is accumulated and recorded, with the scanning means scanning the excitation light whose beam diameter on the surface of the stimulable phosphor sheet is common regardless of the resolution. In the case where the pixel size is read at a first resolution larger than the beam diameter size of the excitation light, with respect to the reading means that photoelectrically reads the stimulated emission light generated from the stimulable phosphor sheet that has been irradiated with a first scanning speed, and read with excitation light of a first intensity, high-resolution der than the first resolution is, if the pixel size is read at a small second resolution than the beam diameters of the excitation light Is a radiation image reading method comprising a step of performing a control of reading with excitation light having a second scanning speed slower than the first scanning speed and a second intensity lower than the first intensity.